Smooth muscle cell arachidonic acid release, migration, and proliferation are markedly attenuated in mice null for calcium-independent phospholipase A2beta.
Pharmacologic evidence suggests that the lipid products generated by one or more calcium-independent phospholipases A(2) (iPLA(2)s) participate in the regulation of vascular tone through smooth muscle cell (SMC) Ca(2+) signaling and the release of arachidonic acid. However, the recent identification of new members of the iPLA(2) family, each inhibitable by (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one, has rendered definitive identification of the specific enzyme(s) mediating these processes difficult. Accordingly, we used iPLA(2)beta(-/-) mice to demonstrate that iPLA(2)beta is responsible for the majority of thapsigargin and ionophore (A23187)-induced arachidonic acid release from SMCs. Both thapsigargin and A23187 stimulated robust [(3)H]arachidonate (AA) release from wild-type aortic SMCs that was dramatically attenuated in iPLA(2)beta(-/-) mice (>80% reduction at 5 min; p < 0.01). Moreover, iPLA(2)beta(-/-) mice displayed defects in SMC Ca(2+) homeostasis and decreased SMC migration and proliferation in a model of vascular injury. Ca(2+)-store depletion resulted in the rapid entry of external Ca(2+) into wild-type aortic SMCs that was significantly slower in iPLA(2)beta-null cells (p < 0.01). Furthermore, SMCs from iPLA(2)beta-null mesenteric arterial explants demonstrated decreased proliferation and migration. The defects in migration and proliferation in iPLA(2)beta-null SMCs were restored by 2 mum AA. Remarkably, the cyclooxygenase-2-specific inhibitor, NS-398, prevented AA-induced rescue of SMC migration and proliferation in iPLA(2)beta(-/-) mice. Moreover, PGE(2) alone rescued proliferation and migration in iPLA(2)beta(-/-) mice. We conclude that iPLA(2)beta is an important mediator of AA release and prostaglandin E(2) production in SMCs, modulating vascular tone, cellular signaling, proliferation, and migration.
Moon
Sung Ho
SH
Division of Bioorganic Chemistry and Molecular Pharmacology, Endocrinology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Jenkins
Christopher M
CM
Mancuso
David J
DJ
Turk
John
J
Gross
Richard W
RW
D000818:Animals; D001011:Aorta / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002465:Cell Movement; D049109:Cell Proliferation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007476:Ionophores / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009130:Muscle, Smooth; D009578:Nitrobenzenes / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007476:Ionophores; D009578:Nitrobenzenes; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D016718:Arachidonic Acid; D000001:Calcimycin; D054513:Group IV Phospholipases A2; D002118:Calcium